virt-convert: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/virt-convert - from package: python-virtinst

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/virt-convert - from package: virtinst

You may install the required package with command apt-get install {package}

Error in other languages:
virt-convert: bevel nie gevind nie
virt-convert: comandă negăsită
virt-convert: comando não encontrado
virt-convert: commande introuvable
virt-convert: command not found
virt-convert: käsku ei ole
virt-convert: không tìm thấy lệnh
virt-convert: komanda nerasta
virt-convert: Kommando nicht gefunden.
virt-convert: kommandot finns inte
virt-convert: komut yok
virt-convert: nie znaleziono polecenia
virt-convert: níor aimsíodh an t-ordú
virt-convert: no se encontró la orden
virt-convert: no s'ha trobat l'ordre
virt-convert: opdracht niet gevonden
virt-convert: parancs nem található
virt-convert: perintah tidak ditemukan
virt-convert: príkaz nenájdený
virt-convert: příkaz nenalezen
virt-convert: команда не найдена
virt-convert: командата не е открита
virt-convert: 命令找不到
virt-convert: コマンドが見つかりません